A significant concern for people who are thinking about having metal implanted in their bodies – such as an artificial joint or pacemaker – is whether they are or might become allergic to any of the materials used in the implant. An allergic reaction to an implanted metal can range from mild irritation of the skin over the implant to pain and tenderness around the implant. In severe cases, an implanted joint can loosen, or system‐wide symptoms such as rash, hives and joint pain can result. Thus, it is essential to go into metal implantation with as much information about not only the procedure itself and what the recovery period will be like, but also a working knowledge about the possibilities of developing symptoms due to metal allergy as well as what to do about it.

How many people have a metal allergy? Allergy to at least some metals is relatively common. When someone says that they can’t wear inexpensive jewelry, that usually means that they are allergic to nickel, and get a rash whenever their skin comes in contact with any metals that contain nickel. Unfortunately, unlike allergies to airborne proteins like pollen and animal danders, there is no way to treat for metal allergies. Instead, patients have to avoid the metal(s) to which they react. For example, people with nickel allergy may wear jewelry that is made of silver or gold, because allergies to these metals are much less common. However, it is a much bigger deal when someone becomes allergic to an implanted metal because the only way to make the symptoms go away is to remove the offending metal. We want to do everything we can to avoid swapping out an artificial knee or hip because it is causing an allergic reaction!

Testing is best performed two weeks before surgery to determine if a given patient has an allergy to any metals that may be implanted. We have done extensive research into the types of materials used in various specialties – orthopedics, cardiology, dental, and gynecology. When an implant by any of these specialists is considered, it is helpful to test at a minimum to the materials that are intended to be implanted. Preferably, the patient will opt to receive testing for the entire panel of relevant materials. For example, if a patient is going to receive an artificial hip, we would test all of the materials used in orthopedics. That way, if a patient is shown to be allergic to the metal being considered, we have already tested them to the alternatives, so the surgeon can choose an alternative material to which no reaction occurred.

What if something happens after implantation?

If a patient shows signs of an allergic reaction after implantation, testing can be used to confirm the allergy. However, a problem with this process is the potential for false positives. This happens when a patient has a positive allergy test to something to which the patient isn’t truly allergic. Due to the potential for false positives, it is always a good idea to do patch testing before implantation. For example, let’s say someone has a problem with a titanium knee. The patient is experiencing pain, but there is no evidence of significant inflammation. If we do metal allergy testing and it is positive for titanium, is that a false positive, or is the patient genuinely allergic to titanium? This is a big deal because if the patient is not truly allergic to titanium, there is just something minor wrong with the joint and the surgeon can address it. If the problem truly is an allergy to titanium, the patient has to get the joint removed and replaced – there are no alternatives. If we didn’t do testing before the implant, it is hard to know if the positive test is a false positive. However, if we did do metal allergy testing before implantation, and the patient tested negative to titanium at the time and now has a positive test, converting from negative to positive makes it much more likely that a developing allergy truly is the problem, and we now know that the joint needs to be replaced.